Hayden Wesneski's New Arsenal Looks Good, But Will It Work Long-Term?

The book on Hayden Wesneski is well-known by now: he completely owns opposing righties, but he gets owned by lefties. In 134 at-bats against opposite-handed batters in 2023, he gave up a .313/.374/.649 slash line. That’s a 1.023 OPS. In other words, lefties facing Wesneski had a higher OPS than Ronald Acuña Jr., the National League MVP. In contrast, righties only slashed .202/.269/.348 against “Wesnasty,” in 173 at-bats, meaning the average righty hit him about as well as Luis Torrens (who had a .618 OPS for the Cubs in 2023).

Going into this season, the pitch mix for Wesneski was also familiar, as he primarily throws a fastball (including a sinker and cutter), a changeup, and his sweeper. That sweeper performed fine against lefties: he threw 158 last year to lefties, yielding a .200 batting average against and .400 slugging percentage against. However, his fastball is a problem: in 220 fastballs thrown to lefties, Wesneski gave up a .387 batting average and a .790 slugging average. In contrast, those pitches have performed admirably against opposing righties (the sweeper generated a .086 batting average in 298 pitches, and the fastball accrued a .237 average across 166 pitches). 

A righty can't just throw the sweeper (usually a pitch with pronounced platoon splits) in lieu of heaters to lefty batters. Thus, it was clear Wesneski needed to tinker with his arsenal to get the hard stuff past them. And just one major-league appearance into his 2024 season, it appears as though Wesneski has gone with the “Occam's Razor” approach: the simplest answer is usually the right one.

That graph is pretty stark, even with the small sample size. Wesneski threw four innings of shutout ball against the Arizona Diamondbacks before being sent back to Triple-A Iowa, relying on just his four-seam fastball and sweeper to get the job done. It was an inspiring performance, especially since he rescued Jordan Wicks from trouble in the fifth and saved a taxed bullpen plenty of bullets. Manager Craig Counsell sure loved it.

Limiting his arsenal to just his two best pitches (and a sparingly-used changeup) is an interesting tactic, though perhaps one born out of limited preparation time. Taylor McGregor spoke with Wesneski after his appearance, at which point the right documented a wild story on how he arrived in Arizona mere hours before the start of the game:

“At 1 AM, my roommate, Matt Mervis, is knocking on my door and Matt’s like hey, you need to call Marty Pevey, the manager for Triple-A," Wesneski recounted. "So I go get my phone, it’s missed calls, text messages, whatever. I call Marty at 1 AM, and he says, ‘Hey buddy, you’re going to the big leagues.’ So I packed for an hour, tried to get some sleep, but didn't… So me and [relief pitcher] Colten Brewer leave at 4 AM to get to the airport in Des Moines. We fly to Chicago because they don’t have any direct flights. Chicago to here [Arizona]. I get here an hour and a half before the game. And then I threw [four shutout innings].”

Still, it’s possible this is Wesneski’s plan moving forward. Cutting the fat from his pitch mix by eliminating his two weaker fastballs isn’t counterintuitive by any stretch, though it makes one wonder if he can get by in the majors throwing just two pitches. Plenty of relievers do it, though they tend to throw much harder than Wesneski. Almost no starters have three or fewer pitches, and the only relatively successful one from the last few years is the Cleveland Guardians’ Triston McKenzie. Wesneski's fastball did sit 95 and scrape 98 in Arizona, too, furthering the case he began to build last year: that he can throw considerably harder as a reliever.

We know the Cubs are keeping Wesneski stretched out as starting pitching depth at Triple-A, so it’s not like he’s definitely being converted to relief. Can such a limited repertoire work in more extended appearances? Can he continue to fool hitters a second and third time through a lineup with just two (or three) pitches?

The answers to those questions remain to be seen, but it’s at least evident that Wesneski isn’t resting on his laurels. He isn’t far removed from being a fringe-Top 100 prospect, and his sweeper is still among the more tantalizing individual pitches in the Cubs’ system. Perhaps with a little more refinement, Wesneski can have some sustained major-league success with a limited cache of pitches.